KVStore: Add comments and refine logging about WaitCheckRegionReady

[JaySon-Huang]

What problem does this PR solve?

Issue Number: ref #6233

Problem Summary:

What is changed and how it works?

• Log the logging as warning level when WaitCheckRegionReadyImpl take more than 60 seconds
• Add keyspace to Region::getDebugString
• Add some comments
• Fix the time unit is wrong in logging introduced by KVStore: Enhance Parallel Prehandle #9155

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

None

[CalvinNeo]

lgtm

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: CalvinNeo, Lloyd-Pottiger

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-06-24 06:27:02.558834579 +0000 UTC m=+614549.044323403: ☑️ agreed by CalvinNeo.
• 2024-06-24 06:30:02.781070672 +0000 UTC m=+614729.266559500: ☑️ agreed by Lloyd-Pottiger.